2012 BRZ/FR-S Stock Class Autocross Discussion

[Evil86]

The Phoenix scca autox club (azsolo.com) runs summer events in Taylor, AZ (northern AZ between Flagstaff and the Border). My fastest clean run was 47.177. This one was dirty, I clipped the 2nd to last cone, but I felt good.

fastest run Taylor.avi - YouTube

sorry the vid sux, youtube said it was "shaky" and offered to "fix it," unfortunately it distorted the video.

Hankooks rs3 41psi front 37psi rear. Next tires will be star specs 225s.

Also I managed to spin the car on one run. I shifted into second as I went around the first slalom on a different run, and it got away from me.

The car is a blast autoxing. I have had three co drivers over three events, and they all dig the car.

[Kido1986]

Low turnout?

Our events are way too crowded lol

[NYC BRZ]

I'm on 225/45/17 star specs and they are fantastic. Had a bunch of great runs yesterday but needed to play more with pressures. It was about 105 on the Tarmac so I was spraying a lot of water. Once the edges were scrubbed in the car came alive.

[dwx]

Originally Posted by des

What are you running for pressures?

I'm on 235/45/17 Star Specs -- a lot more tire than most people are running -- but the rear really settled down and tire temps evened out when we dropped them to 30.

What tires are you on?

Is this on 17x7 rims? Why would you run 235/45 instead of 235/40 or is it just a typo? the 235/45 is a lot heavier than the 235/40 and the gearing is much worse...

I have heard the star specs have a stiffer sidewall so 235/40 on a 7" rim may not be terrible although it will be pinched.

[AlanLGuy]

Originally Posted by NYC BRZ

I'm on 225/45/17 star specs and they are fantastic. Had a bunch of great runs yesterday but needed to play more with pressures. It was about 105 on the Tarmac so I was spraying a lot of water. Once the edges were scrubbed in the car came alive.

What kind of pressures are you running? I'm on the same setup and have been playing with pressures as well. First event I ran 36F/ 38R and I think that was way too much. Second event I dropped down to 32 / 34 which worked better, but still think there is more to be had.

Honestly though, I need to be fixing my driving before playing with pressures too much. Coming from a front wheel drive celica GT-S, I find I tend to trail brake late into the turn to rotate the rear, rather than using the throttle to help it get around. The end result being too fast of an entry and a slow exit witha ridiculous amount of understeer. (I'm embarrassed to say my average PAX position has dropped slightly in the FR-S despite better tires and a MUCH quicker car)

[NYC BRZ]

Originally Posted by AlanLGuy

What kind of pressures are you running? I'm on the same setup and have been playing with pressures as well. First event I ran 36F/ 38R and I think that was way too much. Second event I dropped down to 32 / 34 which worked better, but still think there is more to be had.

Honestly though, I need to be fixing my driving before playing with pressures too much. Coming from a front wheel drive celica GT-S, I find I tend to trail brake late into the turn to rotate the rear, rather than using the throttle to help it get around. The end result being too fast of an entry and a slow exit witha ridiculous amount of understeer. (I'm embarrassed to say my average PAX position has dropped slightly in the FR-S despite better tires and a MUCH quicker car)

I was running 42F/38R. It was understeering slightly.

[des]

Originally Posted by dwx

Is this on 17x7 rims? Why would you run 235/45 instead of 235/40 or is it just a typo? the 235/45 is a lot heavier than the 235/40 and the gearing is much worse...

I have heard the star specs have a stiffer sidewall so 235/40 on a 7" rim may not be terrible although it will be pinched.

45s on the 17x7s. I would have gone for the 40s but they were backordered.

Not worried about the weight, but agree there's an oomph penalty to the 45s that would be exaggerated by a tight or power course. The upside is an additional 2 mph at the top of second.

It's not just about avoiding the shift -- it's staying off that rev limiter, which is pretty cruel. They don't roll over (stiff sidewall, as you point out), and pyrometer shows we are using all of the tire.

I probably will go for the 40s next set (soon) because our Bay Area venues are smaller.

[feldy]

So not sure why you guys are running such high pressures. Stock pressures work great on the stock alignment. Pryometer said so. I run 225/45/17s on rs3s. Been Acutally running 35 front 32 back for added rear grip. Now on my past car with -2 degrees of camber I had to run 45 front for roll over reasons.

[Biggins]

Originally Posted by feldy

So not sure why you guys are running such high pressures. Stock pressures work great on the stock alignment. Pryometer said so. I run 225/45/17s on rs3s. Been Acutally running 35 front 32 back for added rear grip. Now on my past car with -2 degrees of camber I had to run 45 front for roll over reasons.

Agreed. I thought these pressures seemed really high. I don't think you'd need more than 35F/33R on the Dunlops.

I'm still on the OEM tires and have run 35F/33R, and it's not even close to rolling over... I only ran 34F/32R with the Dunlops on my much heavier BMW for many years with success.

[mrazny]

While those are *probably* too high, remember that RS3's and not Star Specs, pyrometers are super useful but not a catch-all, still need to test, and size matters. Fatter star specs typically like less pressure. 17's will run a little different than 18's, etc.

If you have something this a -> b comparable, bmw on 17x7's in that same size, with hopefully the same camber, then pressure on a lighter car can possibly be dropped.

If pyrometers told the whole story, Andy Hollis wouldn't spend days testing various brands, or even fine tuning his selected one. Ideally you'd have a repeatable slalom and a skidpad at various pressures with recorded temps. Then see if the result helps your times. repeat. repeat. repeat. repeat.

[Evil86]

Originally Posted by Kido1986

Low turnout?

Our events are way too crowded lol

Delightfully so. Our Phoenix events vary between 90 to 150 people, but Taylor events are much smaller. This had the lowest turnout, 22 each day for a mini tour format. Six runs in the morning and six in the afternoon each day. Saturday we were done at 2:00 and Sunday at 12:30.. We could have had more runs each day, but 24 total runs were enough. With the exception of a few noobs, everyone was very experienced.

[Evil86]

I played with tire pressures at the test and tune for the SOPAC super regional at El Toro in Cali. I wanted to start with a stock size tire and see what happened. We ran 215 RS3s. We started high, 45/45 and worked our way down. We ended up with 41F/37R. Since then I have tried a few pounds lower in the tires, and for that specific size in RS3, it works pretty good. While I sucked, my co-driver did a very respectable 3rd in a field of 20 (RTR). This weekend, running the same pressure I was coming close to fast STR times. I tried lowering the pressure to around 36/33 and it sucked. The tires became unpredictable.

Optimum tire pressure is as high as you can go before performance falls off.

[dwx]

I'm still trying to figure out if I want to run RTR or CS.

If I do CS I'm probably going to bite the bullet and run the 245/40/17 BFG R1-S tires. If I do RTR I'll probably end up with the 235/40/17 Star Specs. I've raced on both Hoosiers and street tires before, but not for a few years.

Wheels show up tomorrow...

[Evil86]

Originally Posted by dwx

I'm still trying to figure out if I want to run RTR or CS.

If I do CS I'm probably going to bite the bullet and run the 245/40/17 BFG R1-S tires. If I do RTR I'll probably end up with the 235/40/17 Star Specs. I've raced on both Hoosiers and street tires before, but not for a few years.

Wheels show up tomorrow...

RTR at first. After I learn to drive it at its limits, it'll probably go STX. R-tires, as disposable items, are just too expensive.

[Sccabrz192]

Originally Posted by Evil86

RTR at first. After I learn to drive it at its limits, it'll probably go STX. R-tires, as disposable items, are just too expensive.

Season over season the difference between setup cost for a ST classed car versus stock class including the cost of the tires you run... it doesn't ever add up to saving money. I think if you add up total cost per run, you will find street tires do not really save you much money. We typically get about 100-120 runs on harsh concrete lots (toledo express, peru, lincoln, oscoda) on a set of A6s before they are trashed on the GXP.

I just never got that side of the argument to running a street tire class versus the comp tire classes. If the arguement was, I want to modify my car without making it un-streetable (SP/SM/Beyond classes), I understand that. But really... is a fully prepped ST car really THAT street-able?

[MTeator]

I sure see a lot of ST* cars on trailers or with tire trailers and swapping at the event, even local events

My ES MR2 was pretty cheap as far as stock class goes, probably cheaper than an STS miata. I ruined that when I bought a Tundra and an aluminum trailer though...

Now I'm back to a one car solution so happiness.

[dwx]

Yeah let's not turn this into a street tire versus race tire debate. At the most competitive levels you are going to see RT cars on trailers with dedicated shaved tires. RT will be cheaper than CS but obviously once you move to ST the costs are higher.

I think I've decided to give it a go in CS.

[mrazny]

I think someone should go for a 215/40, whether Star Spec or AD08. 23.8".

Besides the fact that I think people dismiss the AD08 too easily, it tends to run a bit wider. If Andy is onto something with the wheel width versus tread width, running the 235 versus the 215 might be a wash in terms of maximum lateral grip. That's an easy skidpad test. 23.8" versus 24.4" should be an easy call gearing wise too. Obviously it's not the cheapest thing in the world to test unfortunately.

So who here is a trust fund baby and can swing $800 in tires just for fun? You can possibly sell them post test for 70 cents on the dollar...

[feldy]

Ha I was swapping tires at events when I ran ST and I still do even in the RT class. Last year on RS3s I was only able to get 120 runs and 4000 street miles on a set. So this year I have not been driving on them unless I have to.

Originally Posted by MTeator

I sure see a lot of ST* cars on trailers or with tire trailers and swapping at the event, even local events

My ES MR2 was pretty cheap as far as stock class goes, probably cheaper than an STS miata. I ruined that when I bought a Tundra and an aluminum trailer though...

Now I'm back to a one car solution so happiness.

[simpleisbest]

Anyone have an oil recommendation for what we do?
I'm posting here because I don't want any "...if turbo..." type answers.

I'm considering the Toyota OEM full synthetic 0w-20. Seems to be pretty good stuff according to many oil forums and the added/lack of loss of "power" from the lighter weight seems attractive. A bit concerned about high rpm protection (not that we spend the whole run at redline though!!!).

Any thoughts?

[dwx]

I bought some Motul 8100 0w-30. That's somewhat due to my daily driving in more city-like conditions, but I figure for autox it wouldn't hurt to have a slightly higher weight oil.

There are some recommendations in the manual about running a higher weight oil for high load situations. With regards to loss of power, I don't think at temp you are going to see much if anything between a 20W and a 30W when spinning the engine at 5000+ RPM.

I know some guys doing track days have talked about running 50W oil, I don't know if I'd go to that extreme.

[Miniata]

Originally Posted by AlanLGuy

(I'm embarrassed to say my average PAX position has dropped slightly in the FR-S despite better tires and a MUCH quicker car)

That's mainly because OVR doesn't apply any sort of RT PAX multiplier to your times, so the PAX numbers you are seeing are for the straight up CS PAX. I believe some regions use a .975 PAX multiplier on top of whatever stock class PAX you're running with for the RT classes.